Update app.py

app.py

@@ -89,7 +89,9 @@ def generate_video_gpu(
     width, height = int(width), int(height)
     negative_prompt = "" # not applicable in the inference
     print("Predicting video...")
-    generator = torch.manual_seed(seed)
+    generator = None
+    if seed is not None:
+        generator = torch.manual_seed(seed)
     frames: List[PIL.Image.Image] = model(
         prompt=prompt,
         height=height,